Ciliary activity in the mammalian respiratory tract is involved in tracheobronchial clearance. Mucociliary transport is important in lung defenses because the action of the cilia continuously removes from the airways the mucous blanket in which airborne contaminants, dust particles and bacteria are embeded. The mechanism by which cilia accomplish this is not well understood. We propose to obrain direct evidence regarding the beat pattern, metachrony and mechanism of motion of cilia from the mammalian respiratory tract by using high-speed cinematography with Normaski and dark-field optics. For this purpose, several in vitro preparations will be obtained form mammalian respiratory epithelia. These will consist of whole isolated ciliated cells (singly and in groupings) and two model systems consisting of apical portions of ciliated cells (cortices) and single cilia. High-resolution electron microscopy of negatively stained and freeze-dried replicas of the demembranated, ATP-reactivated model systems will allow us to analyze the details of active microtubule sliding. We plan to record the changes which occur in the activity of the cilia in these three types of preparations as a response to pharmacological agents, cations and antibody probes. frame-by-frame analysis of the high-speed film will be accomplished using data acquisition techniques suitable for computer analysis. We also hope to analyze ciliary activity in whole ciliated cells as a response to laser microbeam irradiation. Thus, using ourmodel systems to obtain high-speed cinematographic film in conjunction with the computer analysis of this film and the ultrastructural analysis of active sliding, we should be able to describe the waveform f ciliary beating. This would allow us to undersand the mechanism of fluid propulsion and regulation of ciliary function in mammalian systems and thus represents a systematic analysis of mammalian respiratory ciliary function at the cellular level, which has not been previously attempted. Since ciliary activity is important in a wide range of physiological processes, the precise role cilia play could be explored in these systems free from other physiological responses.